The present invention relates to a rapid acting electromagnetic actuator, and is particularly to a rapid acting electromagnetic actuator for controlling the actuation of servo mechanisms such as solenoid valves, the print heads of teleprinters and the like.
As is known, electromagnetic actuators include an armature connected directly or indirectly, for example through suitable transmission means to the device to be controlled such as, for example, the shutter of a valve, and an electromagnet operable to draw the movable armature towards itself when it is excited. All useful electromagnets of this type substantially comprise a ferromagnetic core of suitable form, for example, a core having a cylindrical or annular or square shape and about which are spirally wound one or more conductive wires, for example, of copper. An electromagnetic actuator of this type, however, has the disadvantage of having a relatively long delay time between the initiation of the field intensity vector H and that of the magnetic induction vector B, due, above all, to the volume of iron which it is necessary to use in the magnet and to the relatively high mass of the electromagnet in relation to the volume or iron. To this delay there is also to be added the delay resulting from the necessity of accelerating the core, which is of relatively large dimensions and, therefore, of equally large mass.
To overcome this disadvantage electromagnets with conical windings have been proposed, the core of an individual magnet of this type being substantially in the form of a stepped pulley, and which type of magnet is used in association with a movable armature which is also conical. In this type of electromagnet actuator the masses involved are, however, still greater than those strictly necessary from the theoretical point of view to allow rapid actuation of the actuator itself. Moreover, such actuators are difficult to construct and can have a relatively high cost, particularly in the case in which the ferromagnetic core of such an electromagnet is to be made by sintering. Finally, there is usually the formation of parasitic currents, principally due to the slowness of actuation of the known electromagnetic actuators which must also be considered.
It is an object of the present invention to provide an electromagnetic actuator of the type described above, but which is free from the disadvantages mentioned, and in particular an actuator of a geometry which allows the masses of the movable armature and the core of the electromagnet, as well as the losses due to the initiation of parasitic currents, to be reduced to a minimum in such a way as to guarantee rapid action of the actuator itself. A further object of the present invention is to provide an electromagnetic actuator a geometry which allows a high magnetic flux linkage between the electromagnet and the movable armature in such a way as to obtain relatively high actuating forces on the armature.